In the context of the invention, dental prostheses are to be understood as meaning all possible forms of dentures, such as prostheses or prosthetic elements as dentures in partly toothed or toothless jaws, as well as artificial teeth, crowns and bridge elements. Fixed prostheses or prosthetic elements are understood as meaning technical dental aids which consist of at least two artificial teeth connected to one another (including the necessary supporting or otherwise functional elements), such elements maintaining their mutual position and distance after removal from the jaw position.
The prostheses or prosthetic elements can--after prior adaptation by appropriately trained technical personnel (dentist, etc.)--either be inserted into the mouth or removed therefrom by the prosthesis wearer himself in a simple manner or be fastened indirectly or directly to the jaw in such a way that they can only be inserted or removed by said technical personnel. The prosthesis may rest on the oral mucous membrane, on residual teeth and/or on dental elements. For fastening or stabilization of the prosthesis, various dental measures or elements can be provided.
A prosthetic part generally consists of artificial teeth which are connected to a support base directly resting on the jaw covered with mucous membrane or which are mounted on the support base. The artificial teeth are usually tooth-colored and, like the support base, which as a rule consists of gum-colored plastic, have a functional and an aesthetic or cosmetic function. For reinforcement, reduction of fractures, stabilization or holding of dental elements or for corresponding reasons, an additional reinforcement may be necessary for the dental prosthesis. The reinforcing framework serving as a support part may be present in prefabricated form or prepared specially for an individual prosthesis, and this framework is as a rule incorporated by polymerization during the production of the dental prosthesis. However, in specific cases, the framework may also be incorporated subsequently into a hardened prosthetic part.
Reinforcements commonly used today are generally in the form of metal frameworks which either rest on the mucous membrane and/or are partly or wholly integrated in the prosthetic part. Various metals or alloys and different production processes are available for the production of these metal frameworks. Although metal frameworks produced in this manner can achieve very high strength and dimensional stability, they have various disadvantages both with respect to application and with respect to production.
Thus, the use of a metal in an aqueous, oral medium which is variously acidic or alkaline depending on eating habits and/or personal disposition give rise in principle to a problem if other metals are also simultaneously used in the oral cavity (for example other dental aids, such as, for example, fastening elements for the prosthesis, etc.). Owing to the different positions of two different metals in the electrochemical series, the saliva, acting as an electrolyte, results in the formation of corrosion currents, and the parts of the less noble metal go into solution. Consequently, the risk of intolerance, which is not inconsiderable owing to the incorporation of metals (especially the metals of subgroup V or VIII), may be increased.
In addition to the danger of biointolerance, metal frameworks for reinforcing dental prostheses give rise to an aesthetic problem since they shimmer through metallically in the case of a thin plastic veneer present, for example, because of space requirements, disturbing the visual impression particularly in anterior regions.
In addition to the metal reinforcing frameworks commonly used today, applications and methods in dental prosthetics are known in which different fiber materials are used for reinforcing the plastics part. Such applications and methods are described, for example, in EP-B1-0230 394, WO 91/11153 or U.S. Pat. No. 5,425,640. Substantially lighter prostheses permanently connected to the support framework can be realized by these methods. The fibers used (polyethylene, aramid and other fibers) are placed however, in a manner just as complicated as that described above, in mechanically shaped cavities in the plastics part of the dental prosthesis and then connected thereto chemically.
The shaping of a support part for a dental prosthesis is generally effected directly on a working model or on a model produced by duplication, in order to adapt it to the desired, individual structure of the prosthesis. When glass fibers or other abrasive fibers are used, it is necessary--as when metallic framework parts are used--to ensure that measures for maintaining the distance of the support part from the gum are taken in order to avoid injuries to the gum or to ensure sufficient comfort during wearing. Usually, in the production of the support part, an intermediate member independent thereof is provided for this purpose between model and fiber layer for maintaining the distance, so that the finished support part subsequently does not rest directly on the gum. Although the risk of injury to the gum is reduced in this way and the comfort during wearing may be improved, on the other hand the introduction and trapping of food residues are possible. Furthermore, two production steps essentially independent of one another have to be tailored to one another during the production of the support part. If corrections subsequently have to be made to such a support part, tearing of and damage to the fiber fabric may occur if, for example, too tight a fit is to be corrected by subsequent grinding.